1. Field of the Invention
The invention relates to the field of sample analysis. More particularly, this invention relates to an apparatus and method for increasing the rate at which microwell plates can be manipulated in performing various experiments. Namely, this invention relates to an apparatus and method of performing a pipetting operation on multiple microwell plates in a compact area.
2. Description of the Related Art
In the field of molecular biology, the process of sequencing nucleic acids has become significant as more and more diseases are linked to genetic abnormalities. The process of identifying genes and their corresponding proteins for potential therapeutic applications is well known.
Other types of molecular biology procedures are also important for therapeutic and research purposes including DNA restriction mapping, DNA probe generation, replication, DNA sample processing, and cycle sequencing. Generally, these procedures involve a substantial number of steps including, without limitation, automated liquid handling, robotic movement of the samples, pipetting of small amounts of many different reagents into a sample, and heating the samples within a given temperature range. These protocols includes a lengthy series of steps which must be performed in the correct order with absolute precision. Further, such assays are often done on multiple samples that require the manipulation of samples in sample carriers in a uniform fashion.
For instance, during clinical analysis of blood chemistry, various reagents and catalysts are mixed with blood samples in given amounts and in particular sequences. This analysis can yield the level of HDL cholesterol, LDL cholesterol, lipids, etc. present in the blood. By having multiple samples in a sample carrier, several samples may be analyzed at any give time. Similarly, in the area of new drug discovery, it is desirable to investigate numerous candidates for therapeutic agents. Given the great number of potential candidates, automated testing is desirable.
Because of the expense of the equipment required to perform these protocols accurately, increasing the throughput of the equipment performing these protocols becomes important for laboratories such as microbiology laboratories. It is desirable to increase the rate at which these protocols are performed while retaining, or even increasing, the quality of performance of the protocols. Automation is one method by which the rate of performing the protocols may be increased. By increasing the rate at which these protocols are performed, the protocols may be performed at a reduced cost.
Regardless of the type of experiment to be performed, sample carriers are generally employed so that more than one sample may be processed at any given time. For example, microwell, or microtitre, plates are generally utilized in these sample analysis protocols. Microwell plates are plastic plates containing uniformly-spaced cavities for holding various liquids. Generally, these commercially available microwell plates contain eight rows of twelve microwells for an industry-standard ninety-six microwell plate, or sixteen rows of twenty-four microwells for an industry-standard three hundred eighty-four microwell plate. Other sizes are also commercially available.
It is generally known to perform a protocol with automation as follows. Multiple microwell plates are stacked in one location. A transfer mechanism transfers one of the microwell plates onto a conveyor. Once the pipetting operation is complete, the conveyor transports the microwell plate to the desired station, e.g. a pipetting station. The conveyor then takes the microwell plate to the next station, and so on until the desired protocol has been performed on that microwell plate. Upon completion, that microwell plate is transferred by another transfer mechanism to a completion area for further processing.
In many experiments, it is important to maintain a constant, or even a germ-free, environment. Thus, it is often desired to enclose the samples and the automation equipment. Therefore, it is often desired to minimize the size of pipetting stations and the rest of the automated laboratory equipment, thus minimizing the size of the area that needs to be enclosed.
Because the pipetting operation is generally an important part of any standard protocol, much effort has been expended by the industry to increase the speed, accuracy, and quality of the pipetting operation, and reducing the size of the pipetting operation.
It is desirable to process a large number of samples in a single procedure. Further, pipetting requires dispensing small volumes of samples and other liquids into small containers which are small targets for the pipette. Thus accuracy and resolution are even more important for utilizing these small microwell cavity targets.
Therefore, it is desirable to have a pipetting station for performing liquid transfers of very small quantities of liquids in such a manner that avoids carryover and evaporation. This desired pipetting station should be modular for use in an automated laboratory. Further, it would be desirable for the pipetting station to be able to process a relatively large number of microwell plates, in a relatively small time. Further, it would be desirable for the pipetting operation to be performed accurately, in a relatively small space. And it would be desirable for the pipetting station to be able multitask such that the pipetting operation could be performed on one microwell tray, while other operations are being performed on other microwell trays. Finally, it is desired that a pipetting station have means to verify that the pipetting operation is being performed on the intended microwell plate, thus improving the quality and integrity of the pipetting operation.
Current pipetting stations, such as the MULTIMEK 96 and the BIOMEK 2000 Workstation, both from Beckman Coulter, Inc., are not capable of handling microwell plates that are stacked on vertically-spaced shelves. Therefore, microwell plates must be placed side by side on a table. However, as the number of microwells to be manipulated increases, the surface area required to spread out these microwell trays becomes prohibitive, especially if the work area is to be enclosed.
Similarly, U.S. Pat. No. 5,443,791 to Cathcart, et. al, discloses such a pipetting station, again with microwell plates that are stored side-by-side in a work area and having a relatively small footprint.
Therefore, there is a need for a pipetting station that can process a relatively large number of microwell plates in a comparatively small area.
Another problem with current pipetting systems is that no method exists for automatically ensuring that the pipette station is pipetting into the correct microwell tray. If a tray is mistakenly placed in the pipetting station, the pipetting station will perform the pipetting function without detecting the wrong microwell tray. Thus, it is desirable to have an automatic system to ensure that the correct microwell tray is being processed by the pipetting station thereby improving the quality control and integrity of the protocol.
Thus, despite years of effort, the method of transferring liquid into sample carriers such as microwell plates continues to be slower, less accurate, larger, and more expensive than would be desired.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.